The biggest competition in your niche didn't register the .net version of his site. What's your play? I guess this might be an ethical question but I'm sketchy on the big picture here. What are your options?

unless you are going to promote it as an independant site and at which point your competitor may start an ICANN dispute which you will lose. What good do you think it will it do you ????

Unless it's a huge company like Coca Cola, I would leave it be. Otherwise, buy the domain and do nothing with it in the hopes the huge company buys it from you at a profit. But of course, all HUGE companies already own all of the domain versions, so I would let it be.